Gas sensors sensitive to different molecules are known. Such sensors are normally not totally selective but have different selectivity patterns. It is known to combine such sensors in order to analyze gas mixtures and odors. By comparing the obtained response patterns with previous test results using a computer remarkably precise results can be obtained regarding the identification, classification and also quantification of gas mixtures and odors.
The combination of a number of sensors and a pattern recognition routine is known as an "electronic nose" [Sensors and Sensory Systems for an Electronic Nose, (J. W. Gardner and P. N. Bartlett, eds.) Nato ASI Series E, vol. 212, Kluwer Academic Publishers, 1992]. Electronic noses have numerous applications within the and food processing industry, medical diagnosis, control of combustion, processes and monitoring of the environment, to mention a few.
Modern computers have improved upon the use of pattern recognition methods to identify the response pattern from different sensor to different odors. Many different sensors are available and in many cases a number of set ups may have to be tested and even combined to provide a correct analysis in the end. This is particularly important since it is not only desirable to know which molecules, but it is also in many cases important to know their actual concentrations. This presents a problem since the sensors may have to detect very small quantities of material or very large quantities of the same. Sensors that are too sensitive will not be able to measure large quantities correctly and sensors that are not sensitive enough will not give any indication at all of low concentrations. Thus, in order to obtain arcuate readings taking into consideration amount, concentration and identification, a versatile electronic nose sensor with a range of selectivities and sensitivities is necessary. Furthermore, the choice of the sensors will depend on the particular application. As a result of the above difficulties the electronic noses of today are not very versatile and may in some instances require very large number of sensors and data power making them rather expensive and slow.
Another problem encountered is the lack of selectivity, that is, many sensors react on many gases almost identically, making it difficult to tell them apart and necessitating additional sensors etc.
The object of the present invention is to provide a method by which the analyzing power of chemical sensor arrays can be expanded and a more exact as well as a more versatile device for the monitoring of gas mixtures and odors.